Power steering pressure test

A pressure test of the power steering system is performed when the customer complains of difficult steering or when there are repeated hose failures. Newer models of vehicles with a hydraulic steering system contain a pressure sensor and through diagnostics, the pressure of the steering fluid in the steering system can be checked and monitored. In vehicles that do not have a pressure sensor, a manometer is connected to the hydraulic part of the steering to measure the pressure of the steering fluid.

A suitable adapter with a valve and pressure gauge is installed on the drain line of the servo system. The working pressure, maximum pressure, and flow rate of the steering fluid are tested. The test checks the operation of the power steering pump, pressure regulator, control valve, pressure piston, and hose.

Power steering pressure tester

Power steering pressure tester

Connecting the pressure gauge is done with the engine off. Raise the vehicle so that the front wheels are off the ground. A container for collecting steering fluid is placed under the steering pump. Then the drain pressure hose is separated from the steering pump. Be careful if the engine is hot because then the power steering fluid is also hot and can be under pressure. It is recommended to wait for a little so that the fluid cools down and the pressure in the hydraulic steering system drops.

An adapter with a pressure gauge is connected to the place of the separated hose. Add steering fluid, and start the engine for 2 minutes to bleed from the steering system. That’s how we prepared for testing.

Start the engine again steering wheel is in the neutral position (wheels in the straight-ahead position). The engine is idle, and the pressure is read from the manometer. When the pressure value is higher than required, check the power steering hoses for restrictions.

Power steering pressure test

Then the valve on the manometer adapter is closed briefly two or three times (no longer than 5 seconds), and the highest measured pressure of the steering fluid is recorded. If the pressure is lower than the specification, the steering fluid supply is low, and the steering pump needs to be checked.

Finally, with the valve open and the engine running, the steering wheel all the way and read the pressure. In the same way, measure the pressure on the second full turn of the steering wheel. The measured pressures on one and the other end stop of the steering wheel should be maximum and equal. If there is maximum pressure on one and lower pressure on the other, replace the control box on the steering rack. If the measured pressures are below the maximum value, replace the servo pump with a new one.

When the pressure drops and the steering fluid cools, remove the manometer adapter and connect the pressure hose to the steering pump. Fluid is added, and the bleed from the steering system. Discarded steering fluid is properly disposed of by regulations for the disposal and storage of hazardous liquids.

If the vehicle has a pressure sensor in the power steering system, the pressure test procedure is the same, except that the pressure gauge is not installed. The pressure state from the sensor is monitored via a diagnostic tool.

To power steering pressure test, follow these steps:

Preparation

Raise the vehicle with a jack so that the front wheels are off the ground. Place the container under the steering pump. Disconnect the drain hose from the steering pump. Install an adapter with a pressure gauge between the pump and the drain hose. Add steering fluid and carry out the procedure to bleed from the hydraulic steering system.

Pressure measurement without turning the steering wheel

Start the engine and let it idle. Place the steering wheel in the zero position. Measure pressure and compare to specification. If the pressure is high, check the hoses for twisting and pinching.

Flow measurement

While the engine is idling and the steering wheel is in zero position, briefly (max 5 seconds) close the valve on the adapter two to three times and read the pressure. Compare the measured pressure with the specification. If the pressure is lower than specified, install a new steering pump.

Pressure measurement when turning the steering wheel

While the engine is idling, turn the steering wheel to one side and measure the pressure. Then turn the steering wheel to the other side all the way and measure the pressure. Compare the obtained results with the specification. If the pressure is maximum at one end and low at the other end, replace the control box. If both pressures are low, install a new steering pump.

Turn off the engine, remove the pressure gauge, insert the removed hose, add oil, bleed and lower the vehicle.

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